PRIOR ART
This invention relates to an apparatus for removing from the blood various wastes, toxic substances, and so on, without application of any mechanical force, such as centrifugation, sedimentation, etc., and without fear of hemolysis. In the apparatus, a portion of the plasma is separated by dialysis and filtration, is cleaned by adsorption, degradation, chemical reactions, etc., and returned to the blood stream.
In the last 30 years, hemodialysis has been established as a good method of treating uremic patients. During these three decades, hemodialysis membranes comprised of a cellulose material have been used. In order to improve performance, various semipermeable membranes were developed and fabricated for use in hemodialysis (Proceedings, Annual Contractors' Conference 3-7, 1970-1974, NIH). Some of these membranes having a pore size less than 0.1.mu. have also been used in so-called ultra filtration systems in which only molecules less than the size of the protein molecules were passed, the retained material with the protein therein being returned directly to the patient, and the material passed by the filter either being discarded or regenerated by chemical adsorbent and then returned to the patient.
A recent breakthrough has been the introduction of hemoperfusion techniques utilizing chemical adsorbents as a means of treating the uremic patient (Yatzidis, H., Nephron, 1:310, 1964). Various chemical adsorbents have since been used and some of the systems have been utilized for the actual treatment of the patients. However, one of the major problems which is always inherent in the use of chemical adsorbents is how to avoid small particles of the chemicals being mixed into the blood stream, since these systems require using direct perfusion of blood over the sorbents.
Techniques of microencapsulation of adsorbents were introduced to avoid this problem and also enhance blood compatibility of adsorbents (Chang, T.M., Science, 146:526). The incorporation of the chemical adsorbents, such as activated charcoal, into membrane materials or incorporating the adsorbents into fibers (Davis, T.A., et al., Proceedings, Annual Contractors' Conference, NIAMD, 7:111, 1974) were also attempted for the same reason.
Activated carbon and resins were also utilized for the treatment of acute hepatic insufficiency. The dramatic effect of this was demonstrated clinically utilizing hemoperfusion over activated carbon microencapsulated with hydrogel materials (Gazzard, B.G., et al., The Lancet, P. 1870, June 29, 1974).
However, whatever the technique utilized at this time, still the carryover of microparticles is one of the major problems associated with this type of system. For these systems, a filter is used. However, the most practical filter at this time which is utilized for extracorporeal circulation is an open mesh of 18 microns or larger. Any particles less than this size will go through the filters. If chemical adsorbents are used repeatedly, certainly many particles will be introduced into the vascular system and remain in the body. This is very hazardous, and it is a very difficult problem to solve, even with microencapsulation or improved packaging techniques (Andrade, J.E., et al., Proceedings, Annular Contractors' Conference, NIAMD, 7:113, 1974).